Self-cleaning film system and method of forming same

ABSTRACT

A self-cleaning film system includes a substrate and a film. The film includes a monolayer formed from fluorinated material and a first plurality of regions disposed within the monolayer and spaced apart from one another such that each of the first plurality of regions abuts, is surrounded by, and is not covered by the fluorinated material. Each of the first regions includes a photocatalytic material. A method of forming a self-cleaning film system includes depositing a monolayer formed from fluorinated material onto a substrate. After depositing, the method includes ablating the monolayer to define a first plurality of cavities therein, wherein each of the first cavities is spaced apart from an adjacent one of the first cavities along the monolayer. After ablating, the method includes embedding a photocatalytic material into each of the first plurality of cavities to form a film on the substrate and thereby form the film system.

INTRODUCTION

The disclosure relates to a self-cleaning film system and to a method offorming the self-cleaning film system.

Devices, such as display systems, are often designed to be touched by anoperator. For example, a vehicle may include a display system thatpresents information to an operator via a touchscreen. Similarly, anautomated teller machine or kiosk may include a display system that isactivated by touch.

Other devices, such as cameras and eyeglasses, generally include a lenssurface which may be inadvertently touched by an operator during use.Further, other devices such as vehicles, windows, mirrors, appliances,cabinetry, furniture, cellular telephones, fingerprint scanners,sensors, copiers, medical instruments, and countertops may also includeone or more surfaces which may be touched by an operator. Therefore,during use, an operator may deposit fingerprints and/or oils onto suchdevices and surfaces.

SUMMARY

A film system includes a substrate and a film disposed on the substrate.The film includes a monolayer formed from a fluorinated materialselected from the group consisting of fluorinated organic compounds,fluorinated inorganic compounds, and combinations thereof. The film alsoincludes a first plurality of regions disposed within the monolayer andspaced apart from one another such that each of the first plurality ofregions abuts, is surrounded by, and is not covered by the fluorinatedmaterial. Each of the first plurality of regions includes aphotocatalytic material.

In one aspect, the film may have a first surface and a second surfacespaced opposite the first surface and abutting the substrate. The firstsurface may be substantially free from squalene.

In one aspect, the substrate may have a proximal surface abutting thesecond surface, a distal surface spaced opposite the proximal surface, afirst edge connecting the proximal surface and the distal surface, and asecond edge spaced opposite the first edge. The self-cleaning filmsystem may also include a light source disposed adjacent the first edgeand configured for emitting electromagnetic radiation.

The electromagnetic radiation may have a wavelength of from 400 nm to100 nm. In another aspect, the electromagnetic radiation may have awavelength of from 740 nm to 380 nm. Further, the film may define acontact angle with water of greater than 140°.

In one aspect, the photocatalytic material may be titanium dioxide andmay be present in the first plurality of regions in a rutile form. Inanother aspect, the photocatalytic material may be titanium dioxide andmay be present in the first plurality of regions in an anatase form. Ina further aspect, the photocatalytic material may be titanium dioxideand may be present in the first plurality of regions as a combination ofa rutile form and an anatase form. In yet another aspect, thephotocatalytic material may be doped with silver. The substrate may beformed from silicon dioxide.

In another embodiment, the self-cleaning film system may include asecond plurality of regions disposed within the monolayer such that eachof the second plurality of regions abuts and is surrounded by thefluorinated material, wherein each of the second plurality of regionsincludes silver.

A method of forming a self-cleaning film system includes depositing amonolayer formed from a fluorinated material selected from the groupconsisting of fluorinated organic compounds, fluorinated inorganiccompounds, and combinations thereof onto a substrate. After depositing,the method includes ablating the monolayer to define a first pluralityof cavities therein. Each of the first plurality of cavities is spacedapart from an adjacent one of the first plurality of cavities along themonolayer. After ablating, the method includes embedding aphotocatalytic material into each of the first plurality of cavities toform a film on the substrate and thereby form the self-cleaning filmsystem. The film includes a first plurality of regions including thephotocatalytic material. The first plurality of regions are disposedwithin the monolayer and spaced apart from one another such that each ofthe first plurality of regions abuts, is surrounded by, and is notcovered by the fluorinated material.

In one aspect, the method may further include ablating the monolayer todefine a second plurality of cavities therein.

The method may further include irradiating the first plurality ofregions with electromagnetic radiation having a wavelength of from 400nm to 100 nm. In another aspect, the method may include irradiating thefirst plurality of regions with electromagnetic radiation having awavelength of from 740 nm to 380 nm.

In one aspect, the method may further include contacting the film andsqualene. The method may also include diffusing the squalene along thefilm from the monolayer to at least one of the first plurality ofregions. In addition, the method may also include oxidizing thesqualene. The method may further include vaporizing the squalene.

The above features and advantages and other features and advantages ofthe present disclosure will be readily apparent from the followingdetailed description of the preferred embodiments and best modes forcarrying out the present disclosure when taken in connection with theaccompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a front view of a self-cleaningfilm system.

FIG. 2A is a schematic illustration of a magnified, perspective view ofa portion of the self-cleaning film system of FIG. 1.

FIG. 2B is a schematic illustration of a magnified, perspective view ofa portion of another embodiment of the self-cleaning film system of FIG.1.

FIG. 3 is a schematic illustration of a cross-sectional view of theself-cleaning film system of FIG. 1 taken along section line 3-3.

FIG. 4 is a flowchart of one embodiment of a method of forming theself-cleaning film system of FIGS. 1-3.

FIG. 5 is a schematic illustration of portions of the method of FIG. 4.

DETAILED DESCRIPTION

Referring to the Figures, wherein like reference numerals refer to likeelements, a self-cleaning film system 10 is shown generally in FIG. 1.The self-cleaning film system 10 may be suitable for applications inwhich an operator may touch and deposit fingerprints, oils, and/or otherorganic or carbon-based contaminants or pathogens onto a screen, lens,or surface. More specifically, the self-cleaning film system 10 may beuseful for applications requiring a clean, substantiallyfingerprint-free screen, lens, or surface. That is, the self-cleaningfilm system 10 may be useful for removing fingerprints and other organiccontaminants from such screens, lenses, or surfaces.

For example, the self-cleaning film system 10 may be useful forautomotive applications such as in-dash navigation systems which includea touchscreen, or vehicle cameras which include a lens. Alternatively,the self-cleaning film system 10 may be useful for non-automotiveapplications such as, but not limited to, consumer electronics, cellulartelephones, eyewear, personal protective equipment, appliances,furniture, kiosks, fingerprint scanners, medical devices, sensors,aircraft, and industrial vehicles.

Referring now to FIG. 3, the self-cleaning film system 10 may be appliedto a substrate 12. The substrate 12 may be formed from a vitreous,transparent material suitable for refracting visible light. For example,in one embodiment, the substrate 12 may be formed from silicon dioxide.In another example, the substrate 12 may be formed from a polycarbonateor other plastic. Alternatively, as best shown in FIG. 2A, the substrate12 may be formed from an anti-reflective coating comprising alternatinglayers 14, 16 of silicon dioxide and titanium dioxide. That is, thesubstrate 12 may be an anti-reflective film or coating. In general, thesubstrate 12 may be configured as, by way of non-limiting examples, ascreen of a display system, a lens of eyeglasses or goggles, a visor ofa helmet, a surface of a refrigerator, a face of a cabinet, a door panelof a vehicle, a touchscreen of a kiosk, or as another surface or devicethat may be touched by an operator.

The self-cleaning film system 10 also includes a film 18 disposed on thesubstrate 12, e.g., chemically bonded to the substrate 12 as set forthin more detail below. The film 18 may be configured to cover and protectthe substrate 12 from fingerprints, oils, and organic contaminants. Thatis, the film 18 may be configured to cause fingerprints, oils, andorganic contaminants deposited on the film 18 to vanish, disappear, orvaporize so as to maintain a clean substrate 12 that is capable ofdisplaying crisp images or reflections.

More specifically, as described with reference to FIG. 3, the film 18may have a first surface 20 and a second surface 22 spaced opposite thefirst surface 20. The second surface 22 may abut the substrate 12, andthe first surface 20 may be substantially free from squalene, organicmaterial, and/or other oils of fatty acids. As used herein, theterminology squalene refers to an organic compound having 30 carbonatoms and represented by the International Union of Pure and AppliedChemistry name(6E,10E,14E,18E)-2,6,10,15,19,23-hexamethyltetracosa-2,6,10,14,18,22-hexaene.In general, the film 18 may be characterized as a thin film and may havea thickness 24 of, for example, from 10 μm to 150 μm.

The substrate 12 also has a proximal surface 26 abutting the secondsurface 22 and a distal surface 28 spaced opposite the proximal surface26. Therefore, the substrate 12 and the film 18 are configured totransmit visible light through the proximal surface 26, the distalsurface 28, the first surface 20, and the second surface 22. Thesubstrate 12 also has a first edge 30 connecting the proximal surface 26and the distal surface 28, and a second edge 32 spaced opposite thefirst edge 30.

Referring now to FIGS. 2A and 2B, the film 18 includes a monolayer 34formed from a fluorinated material selected from the group consisting offluorinated organic compounds, fluorinated inorganic compounds, andcombinations thereof. The monolayer 34 may form a majority of the film18 and may be characterized as a monolayer field. As used herein, theterminology monolayer refers to a layer having a thickness 24 (FIG. 2A)of one molecule. That is, the monolayer 34 is one molecule thick and maybe characterized as a thin layer. In one embodiment, the fluorinatedmaterial may be fluorinated diamond-like carbon. In another embodiment,the fluorinated material may be fluorinated tin (IV) oxide. Thefluorinated material, i.e., fluorinated organic compounds, fluorinatedinorganic compounds, and combinations thereof, provides the film 18 withsuperhydrophobicity, anti-microbial properties, anti-soiling properties,and scratch-resistance. The film 18 may also contribute to a clean airquality of an ambient environment in which the film 18 is used.

As shown in FIGS. 2A and 2B, the film 18 also includes a first pluralityof regions 36 disposed within the monolayer 34 and spaced apart from oneanother such that each of the first plurality of regions 36 abuts, issurrounded by, and is not covered by the fluorinated material. That is,the first plurality of regions 36 are situated within and along themonolayer 34. In one embodiment, the first plurality of regions 36 maybe equally spaced apart from each other along the first surface 20. Inother embodiments, the first plurality of regions 36 may be randomlyspaced throughout the monolayer 34 along the first surface 20. In stillother embodiments, the first plurality of regions 36 may be arranged ina pattern within the monolayer 34. The first plurality of regions 36 maybe present in the film 18 in an amount of from about 10 parts by volumeto about 85 parts by volume based on 100 parts by volume of the film 18,e.g., about 50 parts by volume based on 100 parts by volume of the film18.

Each of the first plurality of regions 36 includes a photocatalyticmaterial, such as titanium dioxide. The photocatalytic material mayprovide the film 18 with self-cleaning capability. That is, thephotocatalytic material may oxidize and/or vaporize organic material,e.g., squalene, present on the first surface 20 of the film 18, as setforth in more detail below. In particular, the photocatalytic materialmay be a light-activated photocatalyst upon exposure to, for example,visible or ultraviolet light.

Suitable photocatalytic materials may include, but are not limited to,photo-oxidative semiconductors, semiconducting oxides, doped metaloxides, heterojunction materials, and combinations thereof.

In one embodiment, the photocatalytic material may be titanium dioxideand may be present in the first plurality of regions 36 in a rutileform. Alternatively, the photocatalytic material may be titanium dioxideand may be present in the first plurality of regions 36 in an anataseform, which may exhibit a comparatively higher photocatalytic activitythan the rutile form. In other embodiments, the photocatalytic materialmay be titanium dioxide and may be present in the first plurality ofregions 36 as a combination of the rutile form and the anatase form.Further, the photocatalytic material may be doped to form afunctionalized photocatalytic material, e.g., functionalized titaniumdioxide. For example, the functionalized photocatalytic material may bedoped with a metal such as, but not limited to, chromium, cobalt,tungsten, copper, vanadium, iron, silver, platinum, molybdenum,lanthanum, niobium, and combinations thereof. Alternatively, thefunctionalized photocatalytic material may be doped with a non-metalsuch as, but not limited to, nitrogen, sulfur, carbon, boron, potassium,iodine, fluorine, and combinations thereof. In one example, thephotocatalytic material may be doped with silver. Doping thephotocatalytic material may increase a solar response of thephotocatalytic material, may provide a comparatively higher photonabundance, and may increase a photo-activity of the photocatalyticmaterial.

The photocatalytic material may be characterized as a nanoparticle andmay have an average diameter measureable on a nanometer scale.Alternatively, the photocatalytic material may be characterized as aparticle and may have an average diameter measureable on a micrometerscale. The photocatalytic material may have a thickness of from 1 μm to10 μm. Generally, the photocatalytic material may be present in the film18 in an amount of from about 2 parts by volume to about 35 parts byvolume based on 100 parts by volume of the film 18.

In other non-limiting embodiments, the first plurality of regions 36 mayinclude a semiconducting oxide such as, but not limited to, zinc oxide,bismuth, tin oxide, and combinations thereof. The semiconducting oxidemay be selected to have a band gap separation suitable for aphotocatalytic reaction, as set forth in more detail below.

In another embodiment described with reference to FIG. 2B, the film 18may include a second plurality of regions 38 disposed within themonolayer 34 such that each of the second plurality of regions 38 abutsand is surrounded by the fluorinated material, wherein each of thesecond plurality of regions 38 includes silver. The second plurality ofregions 38 may not be covered by the fluorinated material.

That is, the second plurality of regions 38 may also be situated withinand along the monolayer 34. In one embodiment, the second plurality ofregions 38 may be equally spaced apart from each other along the firstsurface 20. In other embodiments, the second plurality of regions 38 maybe randomly spaced throughout the monolayer 34 along the first surface20. In still other embodiments, the second plurality of regions 38 maybe arranged in a pattern within the monolayer 34. The second pluralityof regions 38 may be present in the film 18 in an amount of from about10 parts by volume to about 85 parts by volume based on 100 parts byvolume of the film 18, e.g., about 25 parts by volume based on 100 partsby volume of the film 18.

The silver may be characterized as a nanoparticle and may have anaverage diameter measureable on a nanometer scale. Alternatively, thesilver may be characterized as a particle and may have an averagediameter measureable on a micrometer scale. Generally, the silver may bepresent in the film 18 in an amount of from about 2 parts by volume toabout 35 parts by volume based on 100 parts by volume of the film 18.The silver may provide the film 18 with soil-resistance, anti-microbial,and air-purifying properties. For example, the silver may disruptmicrobe cellular function. In particular, the silver may contribute tophospholipid decomposition such that a microbe cell well cannot undergorespiration.

Referring again to FIG. 3, the film 18 defines a contact angle 40 withwater of greater than 140°. For example, the film 18 may define acontact angle 40 with water of greater than or equal to 150°. As such,water, oils, and contaminants may effectively bead on and translateacross the first surface 20. Stated differently, water, oils, andcontaminants may be mobile and effectively translate along the firstsurface 20.

The self-cleaning film system 10 may further include a light source 42disposed adjacent the first edge 30 and configured for emittingelectromagnetic radiation. For example, the light source 42 may be anultraviolet light-emitting diode and the electromagnetic radiation mayhave a wavelength of from 400 nm to 100 nm. Alternatively, the lightsource 42 may be an incandescent bulb or a visible light-emitting diodeand the electromagnetic radiation may have a wavelength of from 740 nmto 380 nm.

Referring now to FIGS. 4 and 5, a method 46 of forming the self-cleaningfilm system 10 is illustrated generally. The method 46 includesdepositing 48 the monolayer 34 formed from a fluorinated materialselected from the group consisting of fluorinated organic compounds,fluorinated inorganic compounds, and combinations thereof onto thesubstrate 12. In one embodiment, the method 46 may further includedepositing 48 the monolayer 34 formed from silver onto the substrate 12.By way of non-limiting examples, depositing 48 may include chemicalvapor depositing (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), dipping, wiping, spraying, meniscus coating, wetcoating, combinations thereof, and the like. Depositing 48 may includeforming a self-aligned monolayer 34 that is physically adsorbed, i.e.,physisorbed, and cross-linked with neighboring molecules. In oneexample, depositing 48 may include magnetron sputter depositing agraphite target and a polytetrafluoroethylene target, i.e.,co-sputtering. In another example, depositing 48 may include reactivemagnetron sputter depositing graphite and polytetrafluoroethylene in afluorine-containing gas, such as, but not limited to, difluoroacetylenegas, octafluorocyclobutane gas, tetrafluoromethane gas, andhexafluoropropylene oxide gas, which may contribute to asuperhydrophobicity of the film 18.

That is, the monolayer 34 may be deposited in a suitable manner onto thesubstrate 12 such that the monolayer 34 chemically or physically bondsto the substrate 12. For example, for embodiments in which the substrate12 is formed from silicon dioxide, each molecule of fluorinated materialmay be crosslinked to adjacent molecules of fluorinated material and newchemical bonds may be generated at the proximal surface 26 (FIG. 3) asthe monolayer 34 is deposited onto the substrate 12.

After depositing 48, the method 46 may include ablating 50 the monolayer34 to define a first plurality of cavities 52 (FIG. 5), wherein each ofthe first plurality of cavities 52 is spaced apart from an adjacent oneof the first plurality of cavities 52 along the monolayer 34. In anotherembodiment, ablating 50 the monolayer 34 may also define a secondplurality of cavities 152, wherein each of the second plurality ofcavities 152 is spaced apart from an adjacent one of the secondplurality of cavities 152 along the monolayer 34. As non-limitingexamples, ablating 50 may include laser ablating, plasma ablating,ultraviolet ablating, and the like. Ablating 50 may remove severalmolecules of the fluorinated material monolayer 34 along the proximalsurface 26 to define the first plurality of cavities 52. Similarly,ablating 50 may remove several molecules of the fluorinated materialmonolayer 34 along the proximal surface 26 to define the secondplurality of cavities 152. Generally, the first plurality of cavities 52may extend from the first surface 20 (FIG. 2A) of the film 18 to thesecond surface 22 (FIG. 2A) of the film 18. Similarly, the secondplurality of cavities 152 may extend from the first surface 20 of thefilm 18 to the second surface 22 of the film 18.

After ablating 50, the method 46 may include embedding 54 thephotocatalytic material into each of the first plurality of cavities 52to form the film 18 on the substrate 12 and thereby form theself-cleaning film system 10. Therefore, the film 18 includes the firstplurality of regions 36 (FIG. 2A) including the photocatalytic material.The first plurality of regions 36 are disposed within the monolayer 34and spaced apart from one another such that each of the first pluralityof regions 36 abuts, is surrounded by, and is not covered by thefluorinated material. Similarly, the method 46 may include embedding 54silver into each of the second plurality of cavities 152 to form thefilm 18 on the substrate 12. Therefore, the film 18 may include thesecond plurality of regions 38 (FIG. 2B) including silver and disposedwithin the monolayer 34 such that each of the second plurality ofregions 38 abuts and is surrounded by the silver. The second pluralityof regions 38 may also not be covered by the fluorinated material.

Embedding 54 may include implanting or arranging the photocatalyticmaterial into the monolayer 34 such that the photocatalytic materialforms pillars within the first plurality of regions 36. For example,embedding 54 may include covering portions of the monolayer 34 with amask 57 (FIG. 5) such that photocatalytic material is solely embeddedinto the first plurality of cavities 52 and is not deposited on top ofthe monolayer 34. Suitable processes for embedding 54 the photocatalyticmaterial into the first plurality of cavities 52 to form the firstplurality of regions 36 surrounded by the monolayer 34 include, but arenot limited to, ion beam deposition, atomic layer deposition, chemicalvapor deposition, physical vapor deposition, chemical precipitation,electrophoresis deposition, sputtering, co-sputtering, ion implantation,evaporation, co-evaporation, and pulsed laser deposition.

Embedding 154 may also include implanting or arranging silver into themonolayer 34 such that the silver forms pillars within the secondplurality of regions 38. For example, embedding 154 may include coveringportions of the monolayer 34 with the mask 57 (FIG. 5) such that silveris solely embedded into the second plurality of cavities 152 and is notdeposited on top of the monolayer 34. Suitable processes for embedding54 silver into the first plurality of cavities 52 to form the secondplurality of regions 38 surrounded by the monolayer 34 include, but arenot limited to, ion beam deposition, atomic layer deposition, chemicalvapor deposition, physical vapor deposition, chemical precipitation,electrophoresis deposition, sputtering, co-sputtering, ion implantation,evaporation, co-evaporation, and pulsed laser deposition.

In another embodiment, although not shown, the method 46 includesconcurrently chemisorbing the fluorinated material and thefunctionalized photocatalytic material onto the substrate 12 to form thefilm 18 chemically bonded to the substrate 12 and thereby form theself-cleaning film system 10. The film 18 thus includes the monolayer 34formed from the fluorinated material, and the first plurality of regions36 each formed from the functionalized photocatalytic material and eachdisposed within the monolayer 34 and spaced apart from one another suchthat each of the first plurality of regions 36 abuts, is surrounded by,and is not covered by the fluorinated material. That is, the fluorinatedmaterial and the functionalized photocatalytic material may be depositedonto the substrate 12, simultaneously adsorbed onto the substrate 12,and chemically bonded to the substrate 12. The proximal surface 26 ofthe substrate 12 may concurrently chemically react with the fluorinatedmaterial and the functionalized photocatalytic material to form the film18.

After embedding 54 or concurrently chemisorbing, the film 18 includesthe first plurality of regions 36 formed from the photocatalyticmaterial and spaced apart from one another along the first surface 20(FIG. 3). Such regions 36 may be useful for removing fingerprints fromthe film 18 so that the film 18 exhibits self-cleaning capability. Inanother embodiment, the film 18 may include the second plurality ofregions 38 (FIG. 2B) formed from silver and spaced apart from oneanother along the first surface 20. Such second regions 38 may be usefulfor increasing the anti-fouling and anti-microbial properties of thefilm 18 and may assist with odor removal from an ambient environment.

More specifically, referring again to FIGS. 4 and 5, the method 46 mayfurther include irradiating 56 the first plurality of regions 36 withelectromagnetic radiation having a wavelength of from 400 nm to 100 nm,i.e., irradiating 56 the first plurality of regions 36 with ultravioletlight. Alternatively, the method 46 may include irradiating 56 the firstplurality of regions 36 with electromagnetic radiation having awavelength of from 740 nm to 380 nm, i.e., irradiating 56 the firstplurality of regions 36 with visible light. That is, the light source 42(FIG. 3) may be selected to emit electromagnetic radiation having awavelength tuned to a bandgap of the photocatalytic material to initiatephotocatalysis of the squalene deposited as a fingerprint, as set forthin more detail below. As used herein, the terminology bandgap refers toa difference in energy between the highest permitted energy level for anelectron in a valence band of the photocatalytic material and the lowestpermitted energy level in a conduction band of the photocatalyticmaterial. In other words, the bandgap refers to the minimum amount oflight required to make the photocatalytic material electricallyconductive.

The method 46 may further include contacting 58 the film 18 andsqualene. That is, contacting 58 may include touching the film 18 suchthat an operator deposits fingerprints, squalene, organic matter, and/oroils onto the first surface 20 (FIG. 3). Oils may include oils of fattyacids and may be synthesized naturally and applied to the film 18 as theoperator touches the film 18, or may be applied to the film 18artificially such as by spraying or coating. Contact between thesqualene and the photocatalytic material which is exposed toelectromagnetic radiation emitted by the light source 42 may initiate aphotocatalytic reaction. More specifically, the photocatalytic materialmay be a photocatalyst such as titanium dioxide or titanium dioxidedoped with silver. The photocatalytic reaction may create a strongoxidation agent and breakdown the organic matter, e.g., squalene, tocarbon dioxide and water in the presence of the photocatalyst, i.e., thephotocatalytic material; electromagnetic radiation, e.g., ultravioletlight; and water, e.g., humidity from ambient conditions. As such, thephotocatalytic material not be consumed by the catalytic reaction, butmay instead solely accelerate the photocatalytic reaction as anon-reactant.

In greater detail, when electromagnetic radiation having a desiredwavelength illuminates the photocatalytic material, e.g., titaniumdioxide, titanium dioxide doped with silver, or a mixture of titaniumdioxide nanoparticles and silver nanoparticles, an electron from thevalence band of the photocatalytic material may promote to theconduction band of the photocatalytic material, which in turn may createa hole in the valence band and an excess of negative charge or electronin the conduction band. The hole may assist oxidation and the electronmay assist reduction. Generally, the hole may combine with water toproduce a hydroxyl radical (—OH). The hole may also react directly withsqualene or other organic material to increase an overall self-cleaningefficiency of the film 18. Similarly, oxygen in the ambient environmentsurrounding the photocatalytic material may be reduced by the electronto form a superoxide ion (0.024 which in turn may oxidize the organicmaterial present on the film 18. Therefore, the method 46 may includeoxidizing 60 the squalene. For embodiments including silver, thehydroxyl radical may also decompose a phospholipid portion of a microbecellular wall and cytoplasm wall such that the microbe dies from lack ofrespiration, which may decompose organic matter present on the film 18and contribute to anti-fouling and anti-staining properties of the film18.

In addition, the hole may become trapped before recombination with theelectron. For such situations, the photocatalytic material may befunctionalized. For example, the method may include doping titaniumdioxide with, for example, palladium or ruthenium. The palladium orruthenium may act as an electrocatalyst and may increase a transfer ofelectrons to oxygen molecules, which may in turn lower the occurrence ofthe recombination of electrons and holes.

Further, organic material that is present on the film 18 at themonolayer 34 rather than in direct contact with the first plurality ofregions 36 may be in dynamic equilibrium with the first surface 20 (FIG.3) and may diffuse toward a comparatively higher-energy location on thefilm 18, i.e., the first plurality of regions 36. Therefore, the method46 may also include diffusing 62 the squalene along the film 18 from themonolayer 34 to at least one of the first plurality of regions 36. Toimprove such diffusion, the light source 42 may be tuned to emitelectromagnetic radiation having a wavelength that is tuned to avibration resonance of the squalene and the fluorinated material. Suchtuning may enable the squalene or fingerprint to wiggle or translatealong the monolayer 34 to the first plurality of regions 36 where thesqualene may undergo the photocatalytic reaction described above.Alternatively or additionally, the film 18 may also be heated, forexample by infrared radiation, to further improve diffusion across themonolayer 34 towards the first plurality of regions 36.

As such, the method 46 may further include vaporizing 64 the squalene.More specifically, once the squalene contacts the photocatalyticmaterial at the first plurality of regions 36, the squalene may bephotolyzed into comparatively low vapor pressure-sized pieces or parts,which may vaporize off the film 18 and thereby remove the fingerprint orsqualene from the film 18. Therefore, the self-cleaning film system 10may be characterized as self-cleaning. That is, the film 18 may protectthe substrate 12 by removing, e.g., oxidizing 60 and vaporizing 64, thefingerprints, squalene, oils, and/or organic material deposited by thetouch of an operator. Consequently, the self-cleaning film system 10 andmethod 46 may provide excellent aesthetics, cleanliness, and readabilityfor display systems, lenses, sensors, and surfaces. In particular, thefilm 18 may be comparatively thin, super hydrophobic, transparent,scratch-resistant, durable, tough, and may be a hard coating, i.e., mayhave a hardness of greater than 17.5 GPa and an elastic modulus ofgreater than 150 GPa.

While the best modes for carrying out the disclosure have been describedin detail, those familiar with the art to which this disclosure relateswill recognize various alternative designs and embodiments forpracticing the disclosure within the scope of the appended claims.

What is claimed is:
 1. A self-cleaning film system comprising: asubstrate; and a film disposed on the substrate and including: amonolayer formed from a fluorinated material selected from the groupconsisting of fluorinated organic compounds, fluorinated inorganiccompounds, and combinations thereof; and a first plurality of cavityregions disposed within the monolayer and spaced apart from one anothersuch that each of the first plurality of cavity regions abuts, issurrounded by, and is not covered by the fluorinated material, whereineach of the first plurality of cavity regions includes an embeddedphotocatalytic material.
 2. The self-cleaning film system of claim 1,wherein the film has a first surface and a second surface spacedopposite the first surface and abutting the substrate, and furtherwherein the first surface is substantially free from squalene.
 3. Theself-cleaning film system of claim 2, wherein the substrate has: aproximal surface abutting the second surface; a distal surface spacedopposite the proximal surface; a first edge connecting the proximalsurface and the distal surface; and a second edge spaced opposite thefirst edge; and further including a light source disposed adjacent thefirst edge and configured for emitting electromagnetic radiation.
 4. Theself-cleaning film system of claim 3, wherein the electromagneticradiation has a wavelength of from 400 nm to 100 nm.
 5. Theself-cleaning film system of claim 3, wherein the electromagneticradiation has a wavelength of from 740 nm to 380 nm.
 6. Theself-cleaning film system of claim 1, wherein the film defines a contactangle with water of greater than 140°.
 7. The self-cleaning film systemof claim 1, wherein the photocatalytic material is titanium dioxide andis present in the first plurality of regions in one of a rutile form andan anatase form.
 8. The self-cleaning film system of claim 1, whereinthe photocatalytic material is titanium dioxide and is present in thefirst plurality of cavity regions as a combination of a rutile form andan anatase form.
 9. The self-cleaning film system of claim 1, whereinthe photocatalytic material is doped with silver.
 10. The self-cleaningfilm system of claim 1, further including a second plurality of regionsdisposed within the monolayer such that each of the second plurality ofregions abuts and is surrounded by the fluorinated material, whereineach of the second plurality of regions includes silver.
 11. Theself-cleaning film system of claim 1, wherein the substrate is formedfrom silicon dioxide.
 12. The self-cleaning film system of claim 1,wherein the film comprises greater than or equal to about 2 parts byvolume to about 35 parts by volume of the photocatalytic material basedon 100 parts by volume of the film.
 13. The self-cleaning film system ofclaim 1, wherein the film has a first surface and a second surfacespaced opposite the first surface and abutting the substrate, whereinthe first plurality of cavity regions extends from the first surface tothe second surface.
 14. The self-cleaning film system of claim 1,wherein the fluorinated material comprises a fluorinated diamond-likecoating.
 15. A self-cleaning film system comprising: a substrate; and afilm disposed on the substrate and including: a monolayer formed from afluorinated material selected from the group consisting of fluorinatedorganic compounds, fluorinated inorganic compounds, and combinationsthereof; and a first plurality of regions disposed within the monolayerand spaced apart from one another such that each of the first pluralityof regions abuts, is surrounded by, and is not covered by thefluorinated material, wherein each of the first plurality of regionsincludes a photocatalytic material and wherein the photocatalyticmaterial is functionalized with a dopant selected from the groupconsisting of: chromium, vanadium, lanthanum, nitrogen, carbon, boron,iodine, fluorine, palladium, ruthenium, and combinations thereof.
 16. Amethod of forming a self-cleaning film system, the method comprising:depositing a monolayer formed from a fluorinated material selected fromthe group consisting of fluorinated organic compounds, fluorinatedinorganic compounds, and combinations thereof onto a substrate; afterdepositing, ablating the monolayer to define a first plurality ofcavities therein, wherein each of the first plurality of cavities isspaced apart from an adjacent one of the first plurality of cavitiesalong the monolayer; and after ablating, embedding a photocatalyticmaterial into each of the first plurality of cavities to form a film onthe substrate and thereby form the self-cleaning film system; whereinthe film includes a first plurality of cavity regions including theembedded photocatalytic material; wherein the first plurality of cavityregions are disposed within the monolayer and spaced apart from oneanother such that each of the first plurality of cavity regions abuts,is surrounded by, and is not covered by the fluorinated material. 17.The method of claim 16, further including ablating the monolayer todefine a second plurality of cavities therein.
 18. The method of claim16, further including irradiating the first plurality of regions withelectromagnetic radiation having a wavelength of from 400 nm to 100 nmor having a wavelength of from 740 nm to 380 nm.